Waveguide cooling system for linear accelerator



June 10, 1969 w. .17 GALLAGHER 3,449,618

WAVEGUIDE COOLING SYSTEM FOR LINEAR ACCELERATOR F'ilod July 15, 1966 Sheet of 2 ENERG Y SOURCE HEATER HEAT EXCHANGER F i g. I

COOL FLUID SOURCE INVENTOR. William J. Gallagher Attorneys June 10, 1969 w. J. GALLAGHER WAVEGUIDE COOLING SYSTEM FOR LINEAR ACCELERATOR Sheet Filed July 15, 1966 RF 9 Wm. M m@ J. m .m m w 2 g F Attorneysv United States Patent US. Cl. 3155.41 Claims ABSTRACT OF THE DISCLOSURE A waveguide cooling system for linear accelerator utilizing a plurality of longitudinally extending passageways formed in the waveguide walls and interconnected by annular passageways surrounding the waveguide iris disks.

This invention relates to waveguides for linear accelerators and in particular to such a waveguide including structure for cooling the same.

Heretofore, linear accelerator waveguides have been cooled by circulating fluids in thermal contact with the exterior of the waveguide. Such cooling has not been completely satisfactory in many applications since effective thermal contact is not established with all the members of the waveguide structure especially the iris members thereof. Without effective thermal contact, it is difficult to maintain precise tuning of the waveguide. There is, therefore, a need for new and improved waveguide structure including structure for cooling the same.

In general, it is an object of the present invention to provide a waveguide structure and cooling circuit therein which overcomes the above named limitations and disadvantages.

Another object of the invention is to provide a waveguide structure and cooling circuit of the above character in which the cooling circuit is in intimate contact with a large part of the waveguide structure and in particular with the iris forming disks therein.

Another object is to provide a waveguide and cooling circuit of the above character which, in association with heating means, provides a bake out capability for the waveguide.

Another object of the invention is to provide a waveguide structure and cooling circuit therein of the above character which is self-jigging when assembled and which requires no alignment pins.

These and other objects of the invention will become apparent from the following description in which the preferred embodiment is set forth in detail in conjunction with the accompanying drawing.

Referring to the drawings:

FIGURE 1 is a schematic side view in elevation of the waveguide structure with associated components (shown schematically) and constructed according to the present invention.

FIGURE 2 is an enlarged cross-section view of a portion of the waveguide structure of the FIGURE 1 taken within the lines 22.

FIGURE 3 is a cross-sectional view of the waveguide structure taken along the lines 33 of FIGURE 2.

FIGURE 4 is a cross-sectional view of the waveguide structure taken along the lines 4-4 of FIGURE 2.

Referring now to the drawings. The waveguide 10 comprises a generally elongate tubular shell including a plurality of hollow cylindrical ring-like sections 12 arranged end-to-end in axially abutting alignment with each abutting pair of sections 12 forming a junction therebetween. A disk 13 having an iris aperture 14 therein is mounted transversely at each junction to form together with sections 12 an iris loaded waveguide structure providing a series of coupled electromagnetic cavities 16.

Suitable manifold means 17, hereinafter described in greater detail, couples one end 18 on waveguide structure to an electron gun 19, a source of electromagnetic energy 21, and to a coolant supply piping 22. Other means 23 couples the other end 24 of the waveguide structure to coolant return piping 26. Magnetic means such as a solenoid electromagnet 27 is provided for establishing a magnetic field longitudinally throughout the waveguide structure. The above described arrangement is known in the art of electron linear accelerators to be useful as a slow wave structure for coupling electromagnetic energy to a charged particle beam for accelerating the same. In the form shown, the sections 12 and disks 13 take cylindrically symmetric form in cross-section, but it will be understood that the invention is not so limited but may be used in other geometries, such as rectangular, if appropriate.

Each of the disks 13 is provided with an over-all dimension lying between the inside and outside dimensions of the section 12. The ends of each section 12 are provided with inwardly and longitudinally facing annular recesses 28 and 29 having a diameter approximately the same as the outside diameter of disk 13. Recesses 28, 29 have a combined depth or dimension in the longitudinal direction sufiicient to accommodate the thickness of an interposed disk when adjacent sections are abutted, Thus, recesses 28, 29 cooperate to form an inwardly facing annular groove between adjacent sections for tightly accommodating and aligning an interposed disk at the junction of such adjacent sections.

A plurality of passageways 31 is formed in the wall of each section 12 to extend from one end to the other in longitudinal direction. Preferably passageways 31 are formed intermediate the thickness of the wall and are equally spaced about the wall of the section.

Sections 12 and disk 13 are adapted to cooperate with each other at the junction to form an annular coolant channel 32 thereat and within the wall. Channel 32 communicates with the passageways 31 of each adjacent section so that coolant passes through a channel 32 as it proceeds between the passageways 31 of adjacent sections 12.

The channel is defined by recess 33 provided in one end of each section 12, the opposite end of the next adjacent section and the included disk. More particularly, the recess 33 faces longitudinally and inwardly, being defined by a cylindrical wall 36 at the outside, and a wall 37 by lying in a plane transverse to the structure, wall 37 opening into at least certain of the passageways 31 of the respective section. Thus, the annular coolant channel 32 is defined by walls 36 and 37 of one section, and by the end face 38 of the adjacent abutting section, and inwardly by the outer cylindrical peripheral wall 39 of the included disk.

Sections 12 and disk 13 are assembled together as follows to form a waveguide structure: a first section is selected and disks 13 set into recesses 28 and 29 thereof. A second section is selected and placed over the disk at either end of the first section such that recess 28 and recess 29 of adjacent sections encompass the disk therebetween. Successive sections and disks are added in the same manner until the desired member has been assembled. Suitable braze rings 41 are provided for facilitating permanent joiner of the setcions and disks into unitary structure as by brazing the same together.

Each successive section is preferably angularly shifted or offset with respect to the preceding sections so that the passageways 31 are not in longitudinal alignment whereby coolant passing from one section to the next section is shifted circumferentially about the peripheral wall 39 of the disk as it passes through the waveguide structure. Preferably, each successive section is angularly shifted approximately one-half the angular distance between the passageways so that when the coolant passes through the annular channel 32 it is forced into circumferential motion about the disk and along its entire periphery to thereby provide intimate and uniform cooling action.

To facilitate accurate angular alignment of each successive section, there are provided witness marks (not shown) on the outer wall surface at the ends of ach section, the witness marks at one end being displaced half the angular distance between passageways with respect to that at the other end. Thus, each successive ring is easily located rotationally to its proper angular position by merely aligning the witness marks of adjacent sections.

End 18 of the waveguide structure is then connected to the coolant supply manifold 17 and the other end 24 to a coolant manifold means 23. Each of the manifolds includes an annular member 43 sealably engaging the end of the Waveguide and having a channel 44 therein which communicates with passageways 31 and channel 32, respectively. In a typical installation, manifolds 17, 23 connect through suitable piping 22, 26 to one side of a heat exchanger 47 to form a closed coolant circuit. The other side of heat exchanger 47 is coupled through other piping 48 to a source 50 of cooled fluid.

In operation, the coolant is circulated through the manifolds, waveguide passages 31, and channels 32. After passing through the passages 31 in a respective section 12 and into the channel 32 formed at the other end, the coolant fluid circumferentially passes about the annular perimeter of disk 13, making good thermal contact therewith to provide complete cooling of that section of waveguide. This pattern is repeated through each section of the waveguide to thereby achieve uniform cooling through all parts of the waveguide structure.

Thus there has been shown a particularly effective waveguide structure including a cooling circuit in which coolant is brought in direct thermal contact with each element of the waveguide. Among the advantages of the structure of the invention include the ability to utilize oil as the coolant, which oil can be heated by a heater 52 connected in series in piping 22 to a temperature suitable for baking-out the waveguide. Another advantage of the waveguide structure of the invention results from the use of recesses 28, 29 which accommodate disks 13 therein. In this manner, it is possible to provide a self-aligning waveguide structure in which the various elements are constructed to keep together for proper alignment. In all, the structure of the invention is especially compact and efficient since the cooling circuit is incorporated directly into the walls. By so doing, the bulk of the required associated magnet structure is reduced.

I claim:

1. In a waveguide structure, a plurality of hollow cylindrical sections of substantially the same dimension in cross section, said sections being arranged end-to-end in series abutting relationship with each abutting pair of sections forming a junction therebetween, a disk having an aperture therein mounted at each junction to form with the sections an iris loaded waveguide structure in which a disk is located at the junction of each pair of sections, each of said sections having a plurality of spaced longitudinally extending coolant passageways formed within its wall and extending therethrough from one end to the other, at least one of the sections having an annular recess at one end cooperating with the adjacent end of the next abutting section to form part of an annular cooling channel therebetween which surrounds the interposed disk, said recess and said section opening into at least some of the passageways of the said section, the next adjacent section being annularly offset with respect to the preceding section so that the passageways within said sections are not in longitudinal alignment and so that coolant passing from section to the next section is shifted circumferentially as it passes through said annular recess.

2. A waveguide structure as in claim 1 in which each disk is bounded by an outer annular surface and one wall of the annular channel at each junction is formed by the outer annular surface of the associated disk.

7 3. In a waveguide structure for use in an electron linear accelerator, a plurality of hollow cylindrical sections of substantially the same dimension in cross sections, said sections being arranged end-to-end in a series of abutting relationship with each abutting pair of sections forming a junction therebetween, a disk having an aperture therein mounted at each junction to form with said sections an iris loaded waveguide structure in which a disk is 10- cated at the junction of each pair of sections, each of said sections having a plurality of longitudinally extending cooling passageways formed within its wall and extending therethrough from one end to the other, the sections being arranged so that the passageways in abutting sections communicate with each other, each of said disks having a dimension intermediate the inner and outer transverse dimension of said cylindrical sections, the ends of which are provided with longitudinally and inwardly facing annular recesses having the same diameter as the disk, said recesses cooperating with the next adjacent section to provide a gap therebtween having the same thickness as the thickness of the disk to thereby receive the same and render said waveguide components actually self-aligning when assembled.

.4. In an electron linear accelerator, means forming an iris loaded waveguide structure having longitudinally extending Walls and iris members extending transversely of the walls at regular spaced locations therealong, an elect'ro'n gun, a source of electromagnetic energy, first coolant piping, means for coupling one end of said structure to said electron gun, to said source of electromagnetic energy, and to said first coolant piping, magnet means for establishing an electron confining magnetic field throughout said waveguide structure, said waveguide structure comprising a plurality of hollow cylindrical sections of substantially the same dimension in cross section, said sections being arranged end-to-end in series abutting relationships with each abutting pair of sections forming a junction therebetween, a disk having an aperture therein mounted at each junction to form with the sections an iris loaded waveguide structure in which a disk is located at the junction of each pair of sections, each of said sections having a plurality of spaced longitudinally extending coolant passageways formed within its wall and extending therethrough from one end to the other, at least one of the sections having an annular recess at one end cooperating with the adjacent end of the next abutting section to form part of an annular cooling channel therebetween which surrounds the interposed disk, said recess and said section opening into at least some of the passageways of the said section, the next adjacent section being annularly offset with respect to the preceding section so that the passageways within said sections are not in longitudinal alignment and so that coolant passing from section to the next section is shifted circumferentially as it passes through said annular recess, second 5 coolant piping, means for coupling the other end of said waveguide structure to said second coolant piping, and means for supplying a coolant to one of said coolant pipings and for receiving spent coolant from the other of said coolant piping so that said coolant circulates through the walls of the waveguide structure.

5. An electron linear accelerator as in claim 4 in which a channel is formed in the wall of the waveguide structure and surrounding each iris member, said channel communicating with and interconnecting the longitudinal passageways.

6 References Cited UNITED STATES PATENTS 2,993,143 7/1961 Kelliher et a1. 3155.42 X 3,344,306 9/1967 Levin 31318 X HERMAN K. SAALBACH, Primary Examiner. S. CHATMON, JR., Assistant Examiner.

U.S. Cl. X.R. 

